Iraqis facing an uncertain future in the wake of forcible "regime change" have every reason to fear not only US but also British policy. While past American behaviour in the region is widely criticised, contributing to fears of real US intentions, Britain's role is often regarded as more benign. The reality is that overthrowing governments and backing repressive regimes is as British as afternoon tea.

Fifty years ago, MI6 and the CIA overthrew the popular, nationalist government in Iran, which had threatened British interests by nationalising oil operations. Churchill's government continued covert operations begun by Attlee, to install what foreign secretary Anthony Eden called "a more reliable government". Formerly secret files reveal that our ambassador in Tehran preferred "a dictator" who would "settle the oil question on reasonable terms". The Shah took control and ruled Iran with an iron fist for 25 years, while Britain and the US helped train his secret police.

Britain's invasion of British Guiana in the same year is long forgotten. Democratic elections had resulted in victory for a popular, leftist government committed to reducing poverty. Its plans also threatened the British sugar multinational, Bookers, who pleaded with London to intervene. Britain dispatched warships and 700 troops to overthrow the government, and ruled out elections since "the same party would have been elected again", the colonial secretary stated.

The files also reveal British support for "regime change" in Indonesia in 1965 - one of the worst bloodbaths of the 20th century. "I have never concealed from you my belief that a little shooting in Indonesia would be an essential preliminary to effective change," the ambassador in Jakarta, Sir Andrew Gilchrist, secretly informed the Foreign Office. A million people were killed when the army exterminated the Indonesian Communist Party, PKI.

The Foreign Office stated that "we can hardly go wrong by tacitly backing the generals". London directly aided those engaged in slaughter by conducting covert operations to "blacken the PKI". Britain also delivered secret messages to the army promising not to use its military forces in the region to undermine "the attempts which they now seem to be making to deal with the PKI".

General Suharto removed Sukarno's nationalist government and instigated a brutal military regime, which ruled until 1998, with constant British support.

Syria, Oman, Yemen and Egypt are among other governments targeted by Britain in the last half-century. By invading Iraq, and bombing Afghanistan and Yugoslavia, the Blair government is simply continuing a British tradition of promoting regime change. Looking at these examples, Iraqis should take little comfort. And they should be worried about the other side of the coin: equally indefensible current British policies of promoting "regime support" for favoured governments.

Turkey has destroyed 3,500 Kurdish villages, made hundreds of thousands of people homeless and killed thousands more in its war against Kurds. Atrocities have decreased since the late 1990s but hundreds of thousands of Kurds are unable to return to their villages. Ankara-appointed "village guards" occupy much of their lands; villagers attempting to return have recently been shot dead. Turkish police torture remains systematic.

Britain has been an apologist for these crimes while conducting business as usual. Arms exports flow, while Turkish military officers and the police, guilty of the worst human rights abuses, receive training in Britain. London aided Ankara by closing down the Kurdish TV station, MED-TV, in the same month that BAE Systems, Britain's largest arms company, struck an arms deal with Turkey. Whitehall is bending over backwards to support Ankara's bid to join the EU. Another major Blair ally is Russian President Vladimir Putin. It is instructive that the Foreign Office claims this close official and personal relationship as a great success since it implicates Britain in some of the worst horrors of our time.

The invasion of Chechnya in September 1999 was followed by Russia's flattening of Grozny, killing thousands. British leaders offered the mildest of protests, while defence minister Geoff Hoon spoke of "engaging Russia in a constructive bilateral defence relationship". Human rights atrocities in Chechnya are increasing again, with thousands of "disappearances".

The government refuses to use bilateral levers to press Russia, such as aid or military training. Last year, Blair said of Chechnya, "I have always been more understanding of the Russian position, perhaps, than many others."

The aim of "regime change" and "regime support" is to ensure other governments promote policies favourable to British elites. Basic goals are to shape economies to benefit private corporations and maintain Britain's political status in the world. The concept of "human rights" is generally deployed by leaders as a tool to achieve these objectives. If the past and present in other countries is anything to go by, Iraqis would be wise to challenge British plans for their country and region.

· Mark Curtis's Web of Deceit: Britain's Real Role in the World, is published this month by Vintage.